The present invention relates to a method for vertical connection of conductors in devices, preferably circuit boards, in the microwave range. The method is intended in particular to be applied in antenna constructions.
A common way of building circuit boards is what is known as the multilayer technique, which means that the circuit board consists of a number of layers, where layers comprising a pattern made of an electrically conductive material are arranged on layers of dielectric material. Certain of the layers of electrically conductive material may also be intended to be used as a ground plane, in which case the layer is usually designed as a rectangular plate
For the functioning of the circuit board, it may be necessary to interconnect certain of the various layers at points where it is desirable to have electrical contact. The known ways of making these connections include what are known as coplanar connections and non-galvanic connections. These known ways will be described below.
Coplanar connections can be made either by conductive wires (xe2x80x9cbond wiresxe2x80x9d) or what are known as via-holes. Via-holes are holes which are drilled or made in another manner vertically in the circuit board between the points which are to be connected. The holes are made electrically conductive by being entirely or partly filled with a conductive material. In the case of bond wires, as their name indicates, two points are interconnected by means of wires made of a conductive material. Both these methods for coplanar connections have limitations with regard to the upper operating frequency, which is a distinct disadvantage, above all in applications in the higher microwave range.
Broadly speaking, non-electrical connections are applied exclusively in the microwave range, for connections between conductors which are made using microstrip technology or stripline technology. This type of connection means that two conductors which are to be interconnected are positioned at a certain distance from one another in such a manner that one conductor acts on the other conductor by radiation. Disadvantages of this method of interconnecting conductors are that it results in relatively great losses, and that it has limitations with regard to how great the distance between the two conductors can be.
A disadvantage shared by coplanar connections and non-galvanic connections is moreover that these types of connection are difficult to design so that they give the desired impedance.
A problem which is solved by means of the present invention is therefore that of making a vertical connection between two conductors in a circuit board or another device in the microwave range, where the connection can be designed so that it is imparted a certain impedance which is broadly speaking unaffected by the length of the connection.
Another problem which is solved by means of the present invention is that of making a vertical connection between two conductors in a circuit board or another device in the microwave range, which connection has low losses.
These two problems are solved by means of a method for connection of a first and a second conductor in a circuit board or another device in the microwave range, where each conductor comprises at least one conductive layer, one layer of a dielectric material and one ground plane, where the ground planes of the first and the second conductor are separated from one another in the device by at least a first core made of a dielectric material.
Furthermore, by means of the invention, at least one stage In the manufacture of previously known vertical connections in circuit boards or other electronic devices in the microwave range is eliminated.
According to the method, the various layers in the first conductor, the first core made of dielectric material of the device, and the at least one ground plane and the dielectric layer of the second conductor are arranged on one another in the desired order. A cavity is arranged in the device, extending from fat layer in the first conductor which is to be connected to the second conductor, and at right angles to the main direction of this layer, up to and including that layer in the device on which the conductive layer of the second conductor is to lie.
A component comprising a stripline conductor is arranged in the cavity, The component is arranged so that electrical contact is brought about between the conductor of the component and that layer in the first conductor which is to be connected to the second conductor. Subsequently, the conductive layer of the second conductor and any remaining dielectric layer and any remaining ground plane it has are arranged on the device so that electrical contact is brought about between the conductor of the component and the conductive layer of the second conductor.
The cavity is preferably arranged in the device by each of the layers through which the cavity is to extend having cavities before each respective layer is mounted on the device.
As an altemative, the cavity can be made in the device through the layers through which the cavity is to extend after said layers have been arranged on one another in the desired order.
In a preferred embodiment, the component and the cavity are designed so that, when the component is arranged in the cavity, each of the two ground planes in the stripline conductor of the component will interconnect ground planes in the first and the second conductor. This can of course take place in a number of different ways but is effected in a preferred embodiment by giving the component a design with a central portion which, in the direction In which the conductors are to be connected, projects further at both its ends than two surrounding outer portions.
In a further preferred embodiment the first conductor in the device is a stripline conductor and the second conductor in the device is a microstrip conductor or a stripline conductor.